Existing orders at the Washington Naval Treaty

If Washington allowed all already ordered ships to finish, would Britain demand N3s or leave the treaty?

Probably not; existing G3 orders already help Britain, and an N3 order might be rushed through if needed.

A treaty rule protecting ships already on order would favor Britain because the G3 contracts were on the books. That advantage reduces the need to walk out over the unbuilt N3s. If negotiators saw the rule coming, the Admiralty could rush an N3 authorization through a Royal Dockyard. Such an order would leave no conventional private contract for other delegations to challenge.